We present the development of a technique for studying laser-induced magnetization dynamics, based on inductive measurement. The technique could provide a simple tool for studying laser-induced demagnetization in thin films and associated processes, such as Gilbert damping and magnetization precession. It was successfully tested using a nanosecond laser and NiZn ferrite samples and – after further development – it is expected to be useful for observation of ultra-fast demagnetization. The combination of optical excitation and inductive measurement enables to study laser-induced magnetization dynamics in both thin and several micrometre thick films and might be the key to a new principle of ultrafast broadband UV–IR pulse detection.
Scientists are increasingly specializing in narrower fields, and communication is often difficult between physicists researching elementary particles and those studying semiconductors, not to mention between physicists and biologists or doctors. This makes interdisciplinary work difficult. And yet sometimes they succeed. One thread of work underway at the PAS Institute of High Pressure Physics offers a good example.
The subject of the work is the analysis of thermomechanical bending process of a thin-walled tube made of X5CrNi18-10 stainless steel. The deformation is produced at elevated temperature generated with a laser beam in a specially designed experimental setup. The tube bending process consists of local heating of the tube by a moving laser beam and simultaneous kinematic enforcement of deformation with an actuator and a rotating bending arm. During experimental investigations, the resultant force of the actuator and temperature at the laser spot are recorded. In addition to experimental tests, the bending process of the tube was modelled using the finite element method in the ABAQUS program. For this purpose, the tube deformation process was divided into two sequentially coupled numerical simulations. The first one was the heat transfer analysis for a laser beam moving longitudinally over the tube surface. The second simulation described the process of mechanical bending with the time-varying temperature field obtained in the first simulation. The force and temperature recorded during experiments were used to verify the proposed numerical model. The final stress state and the deformation of the tube after the bending process were analyzed using the numerical solution. The results indicate that the proposed bending method can be successfully used in forming of the thin-walled profiles, in particular, when large bending angles and a small spring-back effect are of interest.
What is the limit of improvement the structure obtained directly from the liquid state, with possible heat treatment (supersaturation and aging)? This question was posed by casting engineers who put arbitrary requirements on reducing the DAS (Dendrite Arm Spacing) length to less than a dozen microns. The results of tests related to modification of the surface microstructure of AlSi7Mg alloy casting treated by laser beam and the rapid remelting and solidification of the superficial casting zone, were presented in the paper. The local properties of the surface treated with a laser beam concerns only a thickness ranging from a fraction to a single mm. These local properties should be considered in the aspect of application on surfaces of non-machined castings. Then the excellent surface layer properties can be used. The tests were carried out on the surface of the casting, the surface layer obtained in contact with the metal mould, after the initial machining (several mm), was treated by the laser beam. It turned out that the refinement of the microstructure measured with the DAS value is not available in a different way, i.e. directly by casting. The experimental-simulation validation using the Calcosoft CAFE (Cellular Automaton Finite Element) code was applied.
Naukowcy specjalizują się w coraz węższych dziedzinach i często trudno się zrozumieć fizykowi cząstek elementarnych z fizykiem półprzewodników, a tym bardziej fizykowi z biologiem czy lekarzem. Dlatego prace interdyscyplinarne są trudne. A jednak czasem się udają. Na przykład uczonym z Instytutu Wysokich Ciśnień PAN.
A system for precise angular laser beam deflection by using a plane mirror is presented. The mirror was fixed to two supports attached to its edges. This article details the theoretical basis of how this deflector works. The spring deflection of a flat circular metal plate under a uniform axial buckling was used and the mechanical stress was generated by a piezoelectric layer. The characteristics of the deformation of the plate versus the voltage control of the piezoelectrics were examined and the value of the change resolution possible to obtain was estimated. An experimental system is presented and an experiment performed to examine this system. As a result, a resolution of displacement of 10-8 rad and a range of 10-5 rad were obtained.
A concept of a highly sensitive and fast-response airborne optoelectronic hygrometer, based on the absorption spectroscopy with laser light tuned to an intense ro-vibronic absorption line of H2O in the 1391– 1393 nm range is presented. The target application of this study is airborne atmospheric measurements, in particular at the top of troposphere and in stratosphere. The cavity ring-down spectroscopy was used to achieve high sensitivity. In order to avoid interference of the results by water desorbed from the instrument walls, the open-path solution was applied. Tests of the instrument, performed in a climatic chamber, have shown some advantages of this concept over typical hygrometers designed for similar applications.
In the paper an example of application of the Kalman filtering in the navigation process of automatically guided vehicles was presented. The basis for determining the position of automatically guided vehicles is odometry – the navigation calculation. This method of determining the position of a vehicle is affected by many errors. In order to eliminate these errors, in modern vehicles additional systems to increase accuracy in determining the position of a vehicle are used. In the latest navigation systems during route and position adjustments the probabilistic methods are used. The most frequently applied are Kalman filters.
In this study, modification of the AZ91 magnesium alloy surface layer with a CO2 continuous wave operation laser has been taken on. The extent and character of structural changes generated in the surface layer of the material was being assessed on the basis of both macro- and microscopy investigations, and the EDX analysis. Considerable changes in the structure of the AZ91 alloy surface layer and the morphology of phases have been found. The remelting processing was accompanied by a strong refinement of the structure and a more uniform distribution of individual phases. The conducted investigations showed that the remelting zone dimensions are a result of the process parameters, and that they can be controlled by an appropriate combination of basic remelting parameters, i.e. the laser power, the distance from the sample surface, and the scanning rate. The investigations and the obtained results revealed the possibility of an effective modification of the AZ91 magnesium alloy surface layer in the process of remelting carried out with a CO2 laser beam.
The aim of the research was to analyze the possibility of using mobile laser scanning systems to acquire information for production and/or updating of a basic map and to propose a no-reference index of this accuracy assessment. Point clouds have been analyzed in terms of content of interpretation and geometric potential. For this purpose, the accuracy of point clouds with a georeference assigned to the base map objects was examined. In order to conduct reference measurements, a geodetic network was designed and also additional static laser scanning data has been used. The analysis of mobile laser scanning (MLS) data accuracy was conducted with the use of 395 check points. In the paper, application of the total Error of Position of the base-map Objects acquired with the use of MLS was proposed. Research results were related to reference total station measurements. The resulting error values indicate the possibility to use an MLS point cloud in order to accurately determine coordinates for individual objects for the purposes of standard surveying studies, e.g. for updating some elements of the base map content. Nevertheless, acquiring MLS point clouds with satisfying accuracy not always is possible, unless specific resolution condition is fulfilled. The paper presents results of accuracy evaluation in different classes of base-map elements and objects.
The base map provides basic information about land to individuals, companies, developers, design engineers, organizations, and government agencies. Its contents include spatial location data for control network points, buildings, land lots, infrastructure facilities, and topographic features. As the primary map of the country, it must be developed in accordance with specific laws and regulations and be continuously updated. The base map is a data source used for the development and updating of derivative maps and other large scale cartographic materials such as thematic or topographic maps. Thanks to the advancement of science and technology, the quality of land surveys carried out by means of terrestrial laser scanning (TLS) matches that of traditional surveying methods in many respects. This paper discusses the potential application of output data from laser scanners (point clouds) to the development and updating of cartographic materials, taking Poland’s base map as an example. A few research sites were chosen to present the method and the process of conducting a TLS land survey: a fragment of a residential area, a street, the surroundings of buildings, and an undeveloped area. The entire map that was drawn as a result of the survey was checked by comparing it to a map obtained from PODGiK (pol. Powiatowy Ośrodek Dokumentacji Geodezyjnej i Kartograficznej – Regional Centre for Geodetic and Cartographic Records) and by conducting a field inspection. An accuracy and quality analysis of the conducted fieldwork and deskwork yielded very good results, which provide solid grounds for predicating that cartographic materials based on a TLS point cloud are a reliable source of information about land. The contents of the map that had been created with the use of the obtained point cloud were very accurately located in space (x, y, z). The conducted accuracy analysis and the inspection of the performed works showed that high quality is characteristic of TLS surveys. The accuracy of determining the location of the various map contents has been estimated at 0.02-0.03 m. The map was developed in conformity with the applicable laws and regulations as well as with best practice requirements.
In this contribution an optical method of controlling the state of soft biological tissues in real time, exposed to laser radiation is discussed. The method is based on the assumption that the change dynamics of the amplitude of the scattered diagnostic radiation (λ = 635 nm) is compatible with the change dynamics of the tissue inner structure exposed to the Nd:YAG laser radiation (λ = 1064 nm). In this method the measurement of the tissue temperature is omitted. Exemplary results of the laboratory research on this method and an interpretation of the results are presented.
Laser triangulation is one of the machine vision measurement methods most commonly used in 3D quality control. However, considering its susceptibility to interference, it cannot be used in certain areas of industrial production e.g. very shiny surfaces. Thus, for the improvement of its applicability, a predictive algorithm of light profile segmentation was designed, where - as a result of using a'priori knowledge - the method becomes resistant to secondary reflexes. The developed technique has been tested on selected parts with surfaces typical for the machine-building industry. The evaluation has been presented based on the surface representation (mapping) error analysis, using the difference between the obtained cloud of points and the nominal surface as processing data, as well as scatter of the discrete Gauss curvature.
The Bulletin of the Polish Academy of Sciences: Technical Sciences (Bull.Pol. Ac.: Tech.) is published bimonthly by the Division IV Engineering Sciences of the Polish Academy of Sciences, since the beginning of the existence of the PAS in 1952. The journal is peer‐reviewed and is published both in printed and electronic form. It is established for the publication of original high quality papers from multidisciplinary Engineering sciences with the following topics preferred: Artificial and Computational Intelligence, Biomedical Engineering and Biotechnology, Civil Engineering, Control, Informatics and Robotics, Electronics, Telecommunication and Optoelectronics, Mechanical and Aeronautical Engineering, Thermodynamics, Material Science and Nanotechnology, Power Systems and Power Electronics. Journal Metrics: JCR Impact Factor 2018: 1.361, 5 Year Impact Factor: 1.323, SCImago Journal Rank (SJR) 2017: 0.319, Source Normalized Impact per Paper (SNIP) 2017: 1.005, CiteScore 2017: 1.27, The Polish Ministry of Science and Higher Education 2017: 25 points. Abbreviations/Acronym: Journal citation: Bull. Pol. Ac.: Tech., ISO: Bull. Pol. Acad. Sci.-Tech. Sci., JCR Abbrev: B POL ACAD SCI-TECH Acronym in the Editorial System: BPASTS.
The paper deals with the basic set-up of single-frequency microchip laser - so called Lyot filter configuration. Description of its operation and practical realization is given. Some results obtained for Nd:YAG/KTP microchip laser are presented. The evidences of single-frequency operation and its limits are emphasized. Described construction constitutes the base for building the frequency stabilization of green 532 nm microchip laser.
Biocompatible coatings produced on the basis of the chemically extracted natural hydroxyapatite (HAp) from the animal bones were deposited using multiplex method comprising glow discharge nitriding (GDN) of the titanium alloy substrate and pulsed laser deposition (PLD) of HAp on the formerly fabricated titanium nitride layer (TiN). The TiN interlayer plays an important role improving adhesion of HAp to substrate and preserves the direct contact of the tissue with metallic substrate in the case of possible cracking of HAp coating. Surface morphology of deposited layers, crystallographic texture and residual stress were studied in relation to the type of laser applied to ablation (Nd:YAG or ArF excimer), laser repetition, temperature of substrate and atmosphere in the reactive chamber.
Strained layer InGaAs/GaAs SCH SQW (Separate Confinement Heterostructure Single Quantum Well) lasers were grown by Molecular Beam Epitaxy (MBE). Highly reliable CW (continuous wave) 980-nm, broad contact, pump lasers were fabricated in stripe geometry using Schottky isolation and ridge waveguide construction. Threshold current densities of the order of Jth ≈ 280 A/cm2 (for the resonator length L = 700 um) and differential efficiency η= 0.40 W/A (41%) from one mirror were obtained. The record wall-plug efficiency for AR/HR coated devices was equal to 54%. Theoretical estimations of above parameters, obtained by numerical modelling of devices were Jth ≈ 210 A/cm and η = 0.47 W/A from one mirror, respectively. Degradation studies revealed that uncoated and AR/HR coated devices did not show any appreciable degradation after 1500 hrs of CW operation at 35oC heat sink temperature at the constant optical power (50 mW) conditions.
Hybryd PLD method was used for deposition high quality thin Ti, TiN, Ti(C,N) and DLC coatings. The kinetic energy of the evaporated particles was controlled by application of variation of di#11;erent reactive and non reactive atmospheres during deposition. The purpose was to improve adhesion by building a bridge between the real ceramic coating and the substrate. A new layer composition layout was proposed by application of a bu#11;er, starting layer. Advanced HRTEM investigation based on high resolution transmission electron microscopy was used to reveal structure dependence on specific atmosphere in the reactive chamber. New experimental technique to examine the crystallographic orientation based on X-ray texture tomography was applied to estimate contribution of the atmosphere to crystal orientation. Using Dictyostelium discoideum cells as a model organism for specific and nonspecific adhesion, kinetics of shear flow-induced cell detachment was studied. For a given cell, detachment occurs for critical stress values caused by the applied hydrodynamic pressure above a threshold. Cells are then removed from the substrate with an apparent first-order rate reaction that strongly depends on the stress. The threshold stress depends on cell size and physicochemical properties of the substrate, but it is not a#11;ected by depolymerization of the actin and tubulin cytoskeleton.
The increasing demands for miniaturization and better functionality of electronic components and devices have a significant effect on the requirements facing the printed circuit board (PCB) industry. PCB manufactures are driving for producing high density interconnect (HDI) boards at significantly reduced cost and reduced implementation time. The interconnection complexity of the PCB is still growing and today calls for 50/50 μm or 25/25 μm technology are real. Existing technologies are unable to offer acceptable solution. Recently the Laser Direct Imaging (LDI) technology is considered as an answer for these challenges. LDI is a process of imaging electric circuits directly on PCB without the use of a phototool or mask. Our laboratory system for Laser Direct Imaging is designed for tracks and spaces on PCB with minimum width distance of 50/50 μm. In comparison with conventional photolithography method, this technology is much better for 50/50 μm track and spaces. In our research we used photoresist with resolution 50 μm, but in case of using laser photoresists with better resolution (e.g. 25 μm) it will be possible to image tracks in super-fine-line technology (25/25 μm). The comparison between two technology of creating mosaic pattern tracks on PCB proved that laser imaging is promising technology in high density interconnects patterns, which are widely use in multilayered PCB and similar applications.
In the recent years three-dimensional buildings modelling based on an raw air- borne laser scanning point clouds, became an important issue. A significant step towards 3D modelling is buildings segmentation in laser scanning data. For this purpose an algorithm, based on the multi-resolution analysis in wavelet domain, is proposed in the paper. The proposed method concentrates only on buildings, which have to be segmented. All other objects and terrain surface have to be removed. The algorithm works on gridded data. The wavelet-based segmentation proceeds in the following main steps: wavelet decomposition up to appropriately chosen level, thresholding on the chosen and adjacent levels, removal of all coefficients in the so-called influence pyramid and wavelet reconstruction. If buildings on several scaling spaces have to be segmented, the procedure should be applied iteratively. The wavelet approach makes the procedure very fast. However, the limitation of the proposed procedure is its scale-based distinction between objects to be segmented and the rest.
In the paper a frequency method of filtering airborne laser data is presented. A number of algorithms developed to remove objects above a terrain (buildings, vegetation etc.) in order to obtain the terrain surface were presented in literature. Those all methods published are based on geometrical criteria, i.e. on a specific threshold of elevation differences between two neighbouring points or groups of points. In other words, topographical surface is described in a spatial domain. The proposed algorithm operates on topographical surface described in a frequency domain. Two major tools, i.e. Fast Fourier Transform (FFT) and digital filters are used. The principal assumption is based on the idea that low frequencies are responsible for a terrain surface, while high frequencies are connected to objects above the terrain. The general guidelines of this method were for the first time presented at (Marmol and Jachimski, 2004). Due to the fact that the preliminary results showed some limitations, two-stage filtering algorithm has been introduced. The frequency filter was modified in such a manner that different filter parameters are used to detect buildings than those to recognize vegetation. In the first stage of data processing the filtering concerning elimination of points connected with urban areas was applied. The low-pass filter with parameters determined for urban area was used for the whole tested terrain in that stage. The purpose of the second stage was to eliminate vegetation by using the filter for forest areas. The presented method was tested by using data sets obtained in the ISPRS test on extracting DTM from point clouds. The results of using the two-stage algorithm were com- pared with both reference data and with filtering results of eight method reported to ISPRS test. A numerical comparison of the filter output with a reference data set shows that the filter generates DTM of a satisfactory quality. The accuracy of DTM produced by the frequency algorithm fits the average accuracy of eight methods reported in the ISPRS test.
Micro-channel heat sinks are used in a wide variety of applications, including microelectronic devices, computers and high-energy-laser mirrors. Due to the high power density that is encountered in these devices (the density of delivered electrical power up to a few kW/cm2) they require efficient cooling as their temperatures must generally not exceed 100 ◦C. In the paper a new design for micro-channel heat sink (MCHS) to be used for cooling laser diode arrays (LDA) is considered. It is made from copper and consisting of 37 micro-channels with length of 9.78 mm, width of 190 μm and depth of 180 μm with the deionized water as a cooling medium. Mathematical and numerical models of the proposed design of the heat sink were developed. A series of thermofluid numerical simulations were performed for various volumetric flow rates of the cooling medium, its inlet temperature and different thermal power released in the laser diode. The results show that the LDA temperature could be decreased from 14 to 17% in comparison with earlier proposed design of the heat sink with the further drop in temperature obtained by applying indium instead of gallium arsenide as the soldering material between the LDA and MCHS interface. Moreover, it was found that the maximum temperature, and therefore the thermal resistance of the considered heat sink, could be decreased by increasing the coolant flow rate.
The paper describes an integrated laser absorption system as a potential tool for breath analysis for clinical diagnostics, online therapy monitoring and metabolic disorder control. The sensors operate basing on cavity enhanced spectroscopy and multi-pass spectroscopy supported by wavelength modulation spectroscopy. The aspects concerning selection of operational spectral range and minimization of interference are also discussed. Tests results of the constructed devices collected with reference samples of biomarkers are also presented. The obtained data provide an opportunity to analyse applicability of optoelectronic sensors in medical screening.
Screw axis measurement methods obtain a precise identification of the physical reality of the industrial robots’ geometry. However, these methods are in a clear disadvantage compared to mathematical optimisation processes for kinematical parameters. That’s because mathematical processes obtain kinematical parameters which best reduce the robot errors, despite not necessarily representing the real geometry of the robot. This paper takes the next step at the identification of a robot’s movement from the identification of its real kinematical parameters for the later study of every articulation’s rotation. We then obtain a combination of real kinematic and dynamic parameters which describe the robot’s movement, improving its precision with a physical understanding of the errors.